Calico cats:
Photos, Pictures, Information

Calico cats are not a breed of cat; calico is a color pattern. To be called "calico", a cat must have black, white and orange in its coat. Variations of these colors include gray, cream and ginger. True calicos have large patches of these three colors, whereas a tortoiseshells or "torties" have a mix of these colors often blended or swirled together, rather than separate blocks of color. The size of the patches can vary from a fine speckled pattern to large areas of colour. Typically, the more white a cat has, the more solid the patches of color. In the UK, these cats are called "tortoiseshell and white". We have more photos of very cute calico kittens.
Long-haired calico cat

Many people are surprised to learn that most cats with this coat pattern are female. This is due to genetics. Coat color in cats is a physical characteristic related to gender. Female animals have two X chromosomes (XX), males have one X chromosome and one Y chromosome (XY). The genetic coding for black or orange coat color is found on the X chromosome. The coding for white is a completely separate gene.
calico cats

Since females have two X chromosomes, they can show two colors (orange and black, or variations of these) and white; creating the 3-color calico mix. Since males have only one X chromosome, they can only be orange OR black. The complex process of dominant and non-dominant genes comes into it too, but that is the basis for coat color in these cats.

I did say that most calicos are female. They can be male in rare instances. In this case, the cat will have two X chromosomes and one Y chromosome (XXY). Cats with this chromosomal composition are usually sterile...is similar to a human condition called Klinefelter's syndrome.

Interesting fact: on October 1, 2001, the calico cat became the official cat of the state of Maryland in the United States.
Sleeping calico cat